446 Mr. A. Ileiifrey on ike Reproduction of the 



LYCOPODIACEiE. 



Two forms of the spore-fruits are known to exist in the species 

 included under the genus Selaginella, the oophoridia producing 

 four large spores, and the antheridia producing a large number 

 of small spores. Both kinds have not been discovered in all the 

 Lycopodiacese ; but in the genus Selaginella in which they do 

 occur, very remarkable facts have been observed in regard to 

 the development of the spores after leaving the spore-fruits. 



The small spores, from the antheridia, after lying a certain time 

 on the damp earth, burst and emit a number of cellules, each of 

 which bursts and discharges a spermatozoid closely resembling 

 that of the Ferns and Equisetacese (PI. XVII. D. fig. 8). 



The large spores when examined soon after their emission from 

 the oophoridia are found to have a layer of minute cellular tissue 

 at the upper end beneath the external tough coat of the spore, 

 and opposite the part where this subsequently bursts open by 

 valve-like flaps (PI. XVII. D. fig. 1). After a time a number of 

 peculiar organs are developed in this cellular expansion or pro- 

 thallium, essentially analogous to the archegonia or ' ovules ' of the 

 Ferns, each consisting of a cellular papilla with a central canal 

 leading down to a free cell lying in a cavity in the prothallium 

 (PI. XVII. B. fig. 2-5). It is presumed that a process of impreg- 

 nation takes place here through the agency of the spermatozoids 

 of the small spores, after the outer coat of the large spore has 

 burst at its apex so as to lay bare the cellular prothallium with 

 its archegonia. The free cell then begins to grow and subdivide, 

 and elongates into a filament which grows down into the cellular 

 tissue which now occupies part of the cavity of the spore. Its 

 terminal cell there becomes developed into a cellular mass 

 (D. fig. 6), upon which a bud with a radicle are soon distin- 

 guishable ; from this bud arises the characteristic leafy stem of 

 the new plant of Selaginella (D. fig. 7), and at the same time an 

 adventitious root grows out (the primary radicle remaining abor- 

 tive) . This embryo, as it may be called, then bursts through the 

 prothallium and grows out into the ordinary forai of the species. 



A similar series of phsenomena have been observed in Isoetes 

 lacustris. The small spores here also produce spermatozoids 'j 

 while the large spores have a prothallium developed within the 

 outer spore-coat, on which archegonia are developed, and in one 

 of these a filamentous suspensor grows down, as in Selaginella, 

 into the cavity of the spore (which here becomes quite filled up 

 with cellular tissue), where it is developed into an embryo with 

 bud and radicle, from which the plant arises and bursts through 

 the coats of the spore. 



The conditions of those Lycopodiacese in which only one kind 



